cmake: Update minimum version to 3.22.1

Matches Vulkan Validation Layers and SPIRV-Tools.

.github/workflows/ci.yml

@@ -21,7 +21,7 @@ jobs:
     strategy:
       matrix:
         os: [ ubuntu-latest, macos-latest ]
-        cmake-version: [ '3.15', 'latest']
+        cmake-version: [ '3.22.1', 'latest']
     steps:
       - uses: actions/checkout@v4
       - uses: lukka/get-cmake@latest
@@ -39,7 +39,7 @@ jobs:
     if: github.event_name != 'pull_request' || github.event.pull_request.head.repo.full_name != github.event.pull_request.base.repo.full_name
     strategy:
       matrix:
-        cmake-version: [ '3.15', 'latest']
+        cmake-version: [ '3.22.1', 'latest']
     steps:
       - uses: actions/checkout@v4
       - uses: lukka/get-cmake@latest

CMakeLists.txt

@@ -5,7 +5,7 @@
 #
 # SPDX-License-Identifier: Apache-2.0
 # ~~~
-cmake_minimum_required(VERSION 3.15)
+cmake_minimum_required(VERSION 3.22.1)
 
 # NOTE: Parsing the version like this is suboptimal but neccessary due to our release process:
 # https://github.com/KhronosGroup/Vulkan-Headers/pull/346
@@ -72,11 +72,6 @@ if (CMAKE_VERSION VERSION_GREATER_EQUAL "3.28" AND VULKAN_HEADERS_ENABLE_MODULE
     target_link_libraries(Vulkan-Module PUBLIC Vulkan-Headers)
 endif ()
 
-if (CMAKE_VERSION VERSION_LESS "3.21")
-    # https://cmake.org/cmake/help/latest/variable/PROJECT_IS_TOP_LEVEL.html
-    string(COMPARE EQUAL ${CMAKE_CURRENT_SOURCE_DIR} ${CMAKE_SOURCE_DIR} PROJECT_IS_TOP_LEVEL)
-endif()
-
 option(VULKAN_HEADERS_ENABLE_TESTS "Test Vulkan-Headers" ${PROJECT_IS_TOP_LEVEL})
 option(VULKAN_HEADERS_ENABLE_INSTALL "Install Vulkan-Headers" ${PROJECT_IS_TOP_LEVEL})
 

tests/integration/CMakeLists.txt

@@ -5,7 +5,7 @@
 #
 # SPDX-License-Identifier: Apache-2.0
 # ~~~
-cmake_minimum_required(VERSION 3.14.2)
+cmake_minimum_required(VERSION 3.22.1)
 
 project(API LANGUAGES C)